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Unfortunately, the P0430 is a fairly straight forward code, with a small diagnostic testing procedure (provided below). This code is saying that the Catalytic Converter for Bank2 (passenger's side) has lost it's ability to store and use oxygen to efficiently clean the emissions from the exhaust, and will need to be replaced. There are a couple of things to be checks, using the diagnostic flow chart below, but, most commonly, this will require a converter replacement.
is the catalytic expensive and where is it located?
Unfortunately, they aren't cheap. You'll need to get as close to Chevy OE as possible, or it will not solve the problem (for example, the "universal" converters sold at AutoZone won't help you one bit). I'm getting a GM Original price list of a little over $600 - but i've had fairly good luck with the "Walker" brand name, for around $400. It's located under the vehicle, as part of the exhaust system. Bank 2 is the passenger's side.